An engine for an automobile generates power by mixing fuel with air introduced from the outside at an appropriate ratio and combusting the mixture.
In order to obtain a desired output and combustion efficiency, it is necessary to supply a sufficient amount of outside air for combustion during a process of generating power by the engine. To this end, a turbocharger is used as an apparatus that supercharges, or pressurizes, the engine with air for combustion in order to improve a combustion efficiency of the engine.
In general, the turbocharger is an apparatus that increases output of the engine by rotating a turbine using a pressure of exhaust gas discharged from the engine and then supplying high-pressure air into a combustion chamber by using a rotational force of the turbine. A turbocharger is applied to many diesel engines, and recently, a turbocharger is also applied to some gasoline engines.
In addition, nitrogen oxide (NOx) included in exhaust gas is considered as a main air pollutant, and research is being conducted to reduce emissions of NOx.
An exhaust gas recirculation (EGR) system is a system mounted in a vehicle in order to reduce various elements in exhaust gas. In general, NOx increases in a case in which a proportion of air in the gaseous mixture is large and thus combustion is smoothly carried out. Therefore, the exhaust gas recirculation system is a system that mixes a part (e.g., 5 to 20%) of exhaust gas discharged from the engine with the gaseous mixture again so as to reduce the amount of oxygen in the gaseous mixture and hinder the combustion, thereby inhibiting the generation of NOx.
As a representative exhaust gas recirculation system, there exists a low-pressure EGR system. The low-pressure EGR system recirculates exhaust gas, which has passed through the turbine of the turbocharger, into an intake passageway at a front end of a compressor.
However, the exhaust gas recirculated by the exhaust gas recirculation system generally has very high temperature and humidity. Therefore, condensate water is produced when the high-temperature recirculating exhaust gas and low-temperature fresh air introduced from the outside are mixed. In this case, the produced condensate water has very high acidity due to various types of substances included in the exhaust gas.
There is a problem in that the condensate water collides with a compressor wheel rotating at a high speed, which causes damage to the compressor wheel. In the related art, in order to prevent the compressor wheel from being damaged, the compressor wheel is coated to prevent damage and corrosion, but there is a problem in that manufacturing costs of the vehicle are increased due to expenses incurred when coating the compressor wheel.
In addition, there are problems in that components, which are disposed at the periphery of the portions where the exhaust gas flows, are corroded due to the condensate water having high acidity, and combustion becomes unstable as the condensate water flows into the combustion chamber of the engine.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.